/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.commons.exec;

/**
 * A default implementation of 'ExecuteResultHandler' used for asynchronous
 * process handling.
 *
 */
public class DefaultExecuteResultHandler implements ExecuteResultHandler {

	/** the interval polling the result */
	private static final int SLEEP_TIME_MS = 50;

	/** Keep track if the process is still running */
	private volatile boolean hasResult;

	/** The exit value of the finished process */
	private volatile int exitValue;

	/** Any offending exception */
	private volatile ExecuteException exception;

	/**
	 * Constructor.
	 */
	public DefaultExecuteResultHandler() {
		this.hasResult = false;
		this.exitValue = Executor.INVALID_EXITVALUE;
	}

	/**
	 * @see org.apache.commons.exec.ExecuteResultHandler#onProcessComplete(int)
	 */
	@Override
	public void onProcessComplete(final int exitValue) {
		this.exitValue = exitValue;
		this.exception = null;
		this.hasResult = true;
	}

	/**
	 * @see org.apache.commons.exec.ExecuteResultHandler#onProcessFailed(org.apache.commons.exec.ExecuteException)
	 */
	@Override
	public void onProcessFailed(final ExecuteException e) {
		this.exitValue = e.getExitValue();
		this.exception = e;
		this.hasResult = true;
	}

	/**
	 * Get the {@code exception} causing the process execution to fail.
	 *
	 * @return Returns the exception.
	 * @throws IllegalStateException
	 *             if the process has not exited yet
	 */
	public ExecuteException getException() {

		if (!hasResult) {
			throw new IllegalStateException("The process has not exited yet therefore no result is available ...");
		}

		return exception;
	}

	/**
	 * Get the {@code exitValue} of the process.
	 *
	 * @return Returns the exitValue.
	 * @throws IllegalStateException
	 *             if the process has not exited yet
	 */
	public int getExitValue() {

		if (!hasResult) {
			throw new IllegalStateException("The process has not exited yet therefore no result is available ...");
		}

		return exitValue;
	}

	/**
	 * Has the process exited and a result is available, i.e. exitCode or exception?
	 *
	 * @return true if a result of the execution is available
	 */
	public boolean hasResult() {
		return hasResult;
	}

	/**
	 * Causes the current thread to wait, if necessary, until the process has
	 * terminated. This method returns immediately if the process has already
	 * terminated. If the process has not yet terminated, the calling thread will be
	 * blocked until the process exits.
	 *
	 * @throws InterruptedException
	 *             if the current thread is {@linkplain Thread#interrupt()
	 *             interrupted} by another thread while it is waiting, then the wait
	 *             is ended and an {@link InterruptedException} is thrown.
	 */
	public void waitFor() throws InterruptedException {

		while (!hasResult()) {
			Thread.sleep(SLEEP_TIME_MS);
		}
	}

	/**
	 * Causes the current thread to wait, if necessary, until the process has
	 * terminated. This method returns immediately if the process has already
	 * terminated. If the process has not yet terminated, the calling thread will be
	 * blocked until the process exits.
	 *
	 * @param timeoutMillis
	 *            the maximum time to wait in milliseconds
	 * @throws InterruptedException
	 *             if the current thread is {@linkplain Thread#interrupt()
	 *             interrupted} by another thread while it is waiting, then the wait
	 *             is ended and an {@link InterruptedException} is thrown.
	 */
	public void waitFor(final long timeoutMillis) throws InterruptedException {

		final long untilMillis = System.currentTimeMillis() + timeoutMillis;

		while (!hasResult() && System.currentTimeMillis() < untilMillis) {
			Thread.sleep(SLEEP_TIME_MS);
		}
	}
}